Modern autorack cars, which is to say autorack cars built since about 1975 for carrying automobiles, trucks or other vehicles in a multiple deck arrangement, have typically had the structure of a flat car underframe covered by a surface defining a main deck for supporting automotive vehicles. Most typically an upstanding elevated-deck supporting framework is mounted to the underframe. Since about 1975 the framework has usually been enclosed within, or used also to support a barn-like housing structure, which may be referred to as a closure system. Closure systems may include side screens, roof, and end closures, typically in the form of movable doors, the better to discourage thieves and vandals. This superstructure is typically referred to collectively as the “rack” of the autorack. Most typically the framework structure includes a series of vertical posts spaced along the sides of the car, with diagonal bracing or shear web panels between the posts, as may be, and one or two additional decks spaced upwardly from the main deck, and upon which respective second and third layers of automotive vehicles may be transported. That is, the rack may be a bi-level rack (i.e., a single elevated deck spaced upwardly above the main deck of the underframe) or a tri-level rack (two upper decks rather than one). The cars tend to be as tall as permitted under the applicable AAR plate clearance diagrams, for this car type, mainly Plate ‘J’ and Plate ‘K’, with maximum heights above Top of Rail or 19′-0″ and 20′-3″ respectively. The housing may tend to have gable ends and bridge plates that are movable to an extended position to span the gap between adjacent cars during loading and unloading. Those end closures, when open, permit circus loading of the cars, i.e., sequential loading of the automotive vehicles by driving in one end, and out the other on arrival. Although other kinds of end closures are known, most typically radial arm doors are mounted at the ends and are movable between open and closed positions to govern loading and unloading of the cars. The racks are typically replaced twice during the economic life of the autorack car underframe. That is, the old rack is removed from the underframe and replaced with a new set of racks.
Dirt and corrosion tend to be problematic in autorack service. First, replacement of the rack superstructure, or merely the deck thereof, is not an inexpensive process. The life-limiting feature of a rack may be corrosion. Rusting of the racks is problematic in two ways. First, rust is a problem for the integrity of the racks themselves. Second, and possibly more important, it is generally undesirable for the racks to drip rusty, or dirty, water on brand-new automobiles being carried as lading. Efforts have been made to limit entry of moisture in to autorack cars. Nonetheless, prevention of the onset of corrosion typically remains desirable. One of the ways to avoid early corrosion is to keep the racks clean, and to reduce the number of locations at which moisture and other contaminants may collect.
In manufacturing, welding soot may tend to collect in every crevice. An approach to this problem is to blast the structure with pneumatically conveyed shot prior to painting. However, the shot blasting process may be imperfect, and it is also desirable that the shot itself not collect in poorly accessible locations in the structure. If not removed the shot may tend to promote poor coating coverage and subsequent corrosion.